Another Michelin tyre query

[Rodders1234]

Due to tyre age I am replacing my 225/75R16CP Agis camper tryes. Because of the pressure (4.5 bar front and 5.5 bar rear) the existing tyres are fitted with metal valves which have built in Fiat tyre pressure monitors.
My question is how do you reset the tyre pressure monitors (these are on the factory fitted displayed on the dash and not TyrePal ones) within the Fiat management system? The tyres are not available at the moment but the fitter tells that in his his experience with other vehicles (not MoHo’s) the system resets itself once you reach 20 miles per hour.

Does anyone have experience of this resetting tyre pressure monitors with a Fiat? Thanks in anticipation.

 

[bb746]

If you are retaining the existing TPMS valves then there is nothing to do (even if the wheels happen to get swapped around).
If you will be fitting new TPMS valves then as long as they are to the correct specification there is still nothing to do as the Fiat system will learn and accept them with 2-3 miles.

 

[maison]

We have a Peugeot based motorhome with their factory fitted TPMS which, if tyres are set to the TPMS pressure, (about 80psi), the ride is very harsh. If set to the pressures recommended by the tyre manufacturer, 56psi front, 62 psi rear, the TPMS warning lights are permanently on.

Being unable to get the system reset by Peugeot or independent garages I asked MMM Magazine for advice.

Their reply is given below. Although my query was re Peugeot they also discuss FIAT.



Please forgive the delay in getting back to you.
Upon receipt of your query, we have been looking into this, contacting manufacturers and asking questions in the after-market. The outcome of this is not encouraging.

We had a reply from Peugeot and they stated that they set the TPMS thresholds at the factory and these form part of the homologation process. These can be set to different levels at the factory if requested to do so by the converter and this change is covered by their homologation process. It seems that if the vehicle is converted in the UK, the settings can be changed by the dealers if they are supported by appropriate final homologation documents from the converter.

What did we learn from this?

That the dealers have the ability to do the change but they are prevented from doing so by Peugeot. If there is any hope of getting this done it would require the converter to instigate it. I think we have to conclude that this is not going to happen.

I have asked a couple of high street tyre businesses and have been told the same thing. They cannot change the thresholds and their diagnostic units have only the ability to 'clone' an existing tpms valve to a new one if needed.

I have looked at this from another point of view. We asked Fiat (as the majority player in the market) and they have not replied at all but using my diagnostic system (Multi-ECUScan) i have been able to deduce that the TPMS is controlled by the Body Computer, or CAN -bus system. There is an option to disable the TPMS and run what is called a 'Proxi-alignment' afterwards that will convince the ECU that TPMS is not present. This would prevent any under or over pressure warnings along with the TPMS warning light illuminating on start-up. Doing this would be contrary to the homologation of the vehicle and in theory render the vehicle not roadworthy. In reality though, the only people that would ever know this would be an MOT tester and since only cars and other passenger vehicles have TPMS as a mandatory fitment; they would not be looking for it anyway.

The Multi-ECUscan device only works on Fiat vehicles and Peugeot have a different main ECU, so i can't know for sure how this would work but the body computers are almost identical to the Fiat ones so any diagnostic that can access the CAN-bus on a Peugeot Boxer should be able to disable the TPMS just as easily. I have spoken to a local Peugeot specialist and he said that he uses Lexia3 which is the Peugeot specific equipment and is certain that he could do as i can with Fiats but he is unsure whether the vehicle would reset to factory defaults when re-started or if the battery is swapped. We definitely need a guines pig vehicle to try it out on!

Failing the above, there are only two other choices available. Live with the warning being on and have with you documentation from the tyre supplier to confirm the reasons for the warning light being on if you are challenged, or follow the advice that i found on YouTube today that showed the TPMS sensors being removed and placed in a sealed container, pressurised to the correct pressure and then being stowed in the vehicle to fool the computer into thinking all is present and correct!

In either of the above, an aftermarket TPMS system could be employed to make sure that you can show diligence and that you are monitoring the pressures indepenently of the on board systems. In the case of the former, you would just have to alter the tyre pressures before an MOT test to ensure that the light is off at that time.

I will be preparing a full and detailed item for the magazine shortly. I will be advising buyers to avoid the option of TPMS entirely while it is not mandatory. Or perhaps insisting that the converter gets the TPMS set at a more reasonable value during the homologation process.

It is surprising that the manufacturers have chosen to use this form of TPMS (known as DIRECT, where TPMS sensors are installed in the wheels) as opposed to INDIRECT which is based on the relative rotational speed of the tyres, employing the ABS sensors. Indirect systems can be reset to whatever pressure you desire. I understand that Ford and BMW emply Direct systems in some of their cars and that these have a resettable feature for the owner; so it seems that a mixture of the benefits of both systems is possible but such decisions are made before manufacture, and cannot be changed.

This is a throny subject and i hope that the above is helpful in some way.

Regards

Nick Fisher
Tech Help Editor
MMM


I hope this is of help.